Stiffness of the hull of a small watercraft greatly affects driving noise. Small watercraft are known with a hull having a sponson made of synthetic resin (see, for example, U.S. Pat. No. 5,908,006). However, conventionally, the sponson has made no contribution in respect of reduction in noise because the sponson made of synthetic resin is light-weight and has low stiffness.
Therefore, a need exists for reducing noise by utilizing the sponson.